Saturday, July 14, 2012

All Great Things Must Come to an End

How can it be that my second field season studying the Northern Goshawk in the Sawtooth National Forest has come to an end? I have a flood of emotions as I consider this prospect. I am sad that my days among the birds has ended. I will miss the ear piercing alarm calls of the adults when I enter their territory. I will miss the sound of the air turbulence as they dive just over my head. I will miss the feel of the wind generated by their wings on the back of my neck! I will miss the suspense of searching for new nesting locations and the joy of discovery when one is found. I will miss the analysis of their subtle behaviors and the challenge of interpreting what their behaviors actually mean. I will even miss the day to day challenges of trudging through the brush counting prey items. I will even miss Badger Gulch!! (the steepest and most rugged of our territories to survey).

I am grateful that I had such an awesome project to work on. I am grateful for the excellent support that I received from the Forest Service, from other awards I have received (Mike Madder's Field Research Award and Michael W Butler Ecological Research Award), from the Boise State University Raptor Research Center, from the Idaho Bird Observatory, and from the BSU Department of Biological Sciences. I am grateful for the excellent members of my team (Lauren, Emmy, and Mike). I am grateful for the many, many volunteers who came to the South Hills to work on the project. Lastly, I am grateful for Karyn's support through all of this project's trials and tribulations.

At the same time, I am very excited for the next phase of this project - the data analysis, manuscript publication, and conference presentations. Yes, it is true, I enjoy this part as well. I have put together an aggressive plan for progress on this front and I can't wait to get started.

This final week of field work consisted of a series of climbs into nests to band the young and collect blood samples for the parasite study. Three nests remained in trees that were safe enough to climb. The climbing duties were once again mine. We also completed our last round of prey surveys and performed habitat surveys in all of the territories. It was a big week!

The climbs. Our first attempt to climb this week was postponed as a result of thunderstorms. This would mean we would need to do multiple climbs per day to complete the work. This was in addition to our full morning of prey surveys each day. On the second day, we finally completed the first climb. To my surprise upon reaching the nest, there were three nestlings instead of two! Bonus. Sometimes from the ground it is difficult to get an accurate count of the birds, even late in the nestling phase.

Mike providing climbing support while I go up the tree. Surprised to find 3 nestlings instead of 2!
Nestling checking out the new arrival - Me!
Got ya!
Goshawk burritos!
Left to right: Emmy taking blood samples, Alexis taking notes, Heidi banding nestlings.
Ahh, smelling the breath of a baby goshawk! Priceless...

The first climb was a success. As we moved toward climb number two for the day, the skies once again began to threaten. We had to cancel. Now I was contemplating cancelling one of the climbs all together as we were running out of time. As we sat in the rain contemplating our plan, a patch of blue sky appeared on the horizon. We scrambled to assemble the team to take advantage of this window of clear skies.

This nest tree is located near a popular campground. As we assembled gear, local campers stopped by to see what we were up to, and once they knew, asked if they could watch. Of course! One of our roles as biologists is to educate the public whenever the opportunity presents itself.

Me explaining my research, what we were doing, and what they should expect.
Nestling staring down at me as I climbed the tree.
Woah! What are you?!? Response as I reached the nest.
Adult female perched nearby watching the spectacle.

The adult female of this nest is banded (note the silver and color band in the above photo). This bird was banded as a nestling by other researchers at Boise State University back in July of 2004. Her identification helps us paint a picture of how far these birds disperse from their natal nests and the general health of the population. We hope that more observations like this will provide us with a more complete picture. This is our primary purpose for banding the young. We now have three high quality data points and with 29 new bands applied this year, hope for quite a few more data in coming years.

Crowd looks on as Mike bands the nestling. I am still hanging in the tree.

The last climb of the week was also a success. This last climb was special as the female was a sub-adult that I banded last year. Generally it is rare for sub-adults to breed, but it has happened on a number of occasions in the South Hills. Last year I had one sub-adult breeder, but the nest failed. Sub-adults often have much lower nest success. The nest with the sub-adult this year looks well poised for success. The single nestling has now reached the age of 30 days old.

More nests? The year has been a spectacular success for goshawks. As of Wednesday we had 17 occupied nests and all are on track to be successful (fledging at least one young). On Thursday, during my final prey survey of the project, I happened upon an 18th occupied nest. The randomly placed survey just happened to pass right by the nest. A single 38 day old nestling stared down at me. Spectacular luck. With the age of this nestling, it is possible there were others that had already left the nest, but I didn't see any. This just proves my point that there are probably a number of additional nests that we don't know about. Every time we look in a new area, we tend to find occupied nests or at least signs of previous nesting activity. Over the past two years, we have established five new territories that were not previously known. I have had detections in three additional areas, but we were unable to either repeat the detection or find evidence of an occupied nest. The goshawks are doing well in the unique forest structure of the South Hills, a location where you might not expect them to be.

Charlie! In previous posts I have told the story of Charlie, a nestling goshawk that we found on the ground and returned to the nest. I am happy to report that Charlie is still kicking and it appears as if he will fledge any day now. His three nest-mates have already left the nest, but he is still being protected and fed by his parents. Here is a video highlighting the departure of his last nest-mate and his first meal alone in the nest. We wish you well Charlie! (video presented in double time)

Next Steps. While the regular field operations are over, the project is far from complete. In a couple of weeks I will return to the South Hills to take down my nest cameras and check status in a few locations. Then comes watching three months of recorded video to quantify the prey consumption by the nestlings. Even with fast forward, that is going to take a while. More data analysis, manuscript generation, manuscript submission, presentation at conferences, etc all follow from there. It should be a fantastic, yet busy journey.

Tuesday, July 03, 2012

The Sharp End of a Goshawk

Talons of a nestling Northern Goshawk.

Welcome to the latest update from my field season studying the Northern Goshawk in the Sawtooth National Forest covering weeks 6 & 7 of my season. It is hard to believe the season is nearly over. Just one full week remaining followed by a short visit a few weeks later. This bout had a great deal of progress to report on, so sit back and enjoy the story.

Previous field updates

Week 1: Oh, What a Great First Week it has Been
Week 2 & 3: As Slow as Possible, As Fast as Necessary
Week 4 & 5: Intimate Encounters with a Northern Goshawk
Week 5: Charlie's First Meal After Returning Home

The project has shifted from performing a lot of surveys and searching for nests, into more extensive monitoring of the individual nests. While we are still searching for nests and performing some prey surveys, this bout of effort was much more focused on the nestlings themselves.

Before getting to the details of our nestling activities, I am happy to report a few significant items that we accomplished this week. First of all, we discovered three more additional occupied nests for a season total of 17. I only had ten last year and two of those had failed by this point in time. Nestlings have hatched in all 17 territories and there have been no nest failures. Hmm, its hard to analyze the factors influencing success/failure rates with no failures... However, this is not a problem that I am going to complain about!

A second great discovery is that I was able to read the band number on the only sub-adult female (1 year old bird) that we have found breeding in the area. Usually females don't breed until they are full adults (2 years old). She was one of the birds that I banded last year as a nestling. I was hoping that it would be "Chuck", but I will accept that "Chuck" is still roaming the skies somewhere and that one of my other banded nestlings is successfully raising her first offspring in this nest.

Half of our effort over the past few weeks has been climbing trees, banding young, and extracting blood samples. The banding process helps us to better understand the dynamics of this population of birds. Is this population of goshawks a population sink (net-negative contribution to the regional population), or a source (net-positive contribution). In the past year we have three new datapoints from banding activities which will help answer this question (including the sub-adult female that I just mentioned). The blood samples are collected for two purposes. The first use is to evaluate the nestlings for Leucocytozoan infection. It has long been hypothesized that the goshawk population suffers from infection by this parasite and that the parasite is having a significant impact on the population by killing the offspring. The parasite is transmitted by Black Flies which are abundant in the South Hills and abundant within the goshawk nests. An undergraduate student, Michelle J, will be heading up this investigation in conjunction with my project. The second use of the blood will be for a yet-unidentified undergraduate researcher to evaluate the genetic diversity of the population for signs of inbreeding depression. A previous study in Arizona found that the genetic diversity is higher there than would be expected given the population size. We would hope for a similar result in the South Hills as the South Hills population, while large, is not large enough to ensure the long term survival without immigration of genetic diversity.

I'm heading up the first of nine nests we processed this week, using the spur and sling approach.

The process may seem simple, but a full team effort is required to successfully climb the trees and keep the birds and the climbers as safe as possible. The first task is for the climber to get up the tree. We generally climb using spurs and then rappel out of the tree. However, we occasionally have "shot a line" through the upper branches of the tree to pull a rope up and climb the rope. If feasible, this method is faster, generally safer, and has a lesser impact on the tree. Unfortunately, on the first few climbs I had to "down-climb" as there were no good rappel anchors.

I arrived at the nest within 4 minutes!

After the climber arrives at the nest, a bag is attached to the rope to transport the nestlings. An elastic sock is placed over the bird to hold the wings in and keep it safe. Sometimes a hood is also placed over the bird's head to decrease stress. The bird is placed into the bag and slowly lowered to the ground.

Mike receives first bird on the ground.

Once on the ground the bird has two bands applied - a silver 9 digit USGS bird band and a Purple color band with a two digit code. The color band allows for remote identification of the bird with binoculars without the requirement to recapture the bird. This is how I identified the sub-adult bird that I mentioned earlier.

Emmy applying silver USGS band to female nestling goshawk.

The bird is carefully passed from the bander to the Phlebotomist to extract the blood samples. A minimal amount of blood is extracted. We extract two drops for analysis of parasites via a blood smear and another 5-10 drops for later genetic analysis.

Michelle L. preparing to collect blood from nestling.

It is then time for the nestling to be returned to the nest. The total time that any bird is out of the nest is usually less than 10 minutes. In fact the whole operation usually takes less than one hour.

I'm getting ready to descend the tree.

There are many other roles within the team besides those highlighted so far. Probably the most important is the watcher which is supposed to warn the climber of an incoming attack from the adults. Some adults are more aggressive than others, but it is always a risk to take seriously. As David noted after taking a number of direct hits from an adult, "On Wednesday I was climbing with a chainsaw, this makes me much more nervous than that!" Other people are needed to record the data, take photos, hold birds, etc. It works best with 5 or 6 people, but can be successful with as few as 4.

Team for the first two climbs: Michelle, Kraig, Emmy, Rob (me), Mike. Not pictured: Thurman the photographer.
Emmy, ... your eyes are the color of a nestling goshawk...

The team dynamics shifted for the weekend. We traded Michelle J for Michelle L as Michelle and Kraig had to return to Boise. Thurman had to return to his job and was thus unavailable. However, we were joined by a new climber, David who had previously helped with camera installation and by Greg and Ayla. It all worked out great.

Ground Crew: Emmy, Michelle J, Mike.
David's view into a four nestling nest.

In a previous post I told the story of "Charlie", the nestling that we had returned to the nest during camera installation. I am happy to report that Charlie and his siblings are all still with us. However, evaluating the developmental stages of the nestlings show that Charlie is up to six to eight days behind his siblings in maturity. While it is possible that he is actually a couple of days younger, he shouldn't be six to eight days younger. Especially since males tend to mature faster than females in the nest. I therefore conclude that Charlie had spent many days on the ground without food before we returned him to the nest. I hope that he continues to be able to compete for food, especially once his siblings leave the nest.

Left to right: Charlie, his two brothers, his big sister. Note the leg size used to sex these birds.

In all, this weekend we climbed in nine nests and banded/bled 24 nestlings. But one nestling eluded us by traveling many feet out onto a branch to avoid our grasp. In honor of his/her ingenuity, Emmy named it "Lou".

Defiant "Lou".
Lou's sister, angry that she wasn't as clever. Note the purple color band.

The bravest climb of the weekend was David's last, an 80 foot Aspen. This tree not only presented challenges with its height, but also with the hot sun, breezy conditions, and getting above the three foot deep nest in the center of the tree. It was impressive to watch and I learned a great deal.

David arriving at the tallest of my 17 nests - 80 feet high.

The great news is that all birds and all crew finished the weekend safe. We have just three nests yet to climb next week before the nestling phase of the project is complete.

Guns. What do field biology and guns have in common, probably more than you would think, but not in a good way. We had two encounters with guns this past week. On the first encounter a man pulls up on his ATV to talk to me, but parks in such a way that his rifle is pointed directly at me. Whether this was an intentional act of intimidation or just clueless irresponsibility, I will never know. After I moved out of his "sights", he was friendly to me although accused most everyone else of being liars. The Fish and Game lie about how many deer are in the South Hills as he can't seem to find them on his ATV. The forest service lies about their intent to not close any roads. I am sure he thought I was lying about ground squirrel abundance as he was upset he had only been able to shoot two that day. After the requisite polite discussion, I extracted myself to get back on the more positive task at hand - finding more goshawk nests.

The second gun incident was much more serious in nature. On one of our climbs, David had just started up the tree. The adult female started her defensive maneuvers by issuing her alarm call and circling overhead. As she circled to the west a loud high caliber pistol shot echoed from about 100-150 meters away. We immediately yelled and the shooting stopped. While we cannot confirm that they were shooting at the goshawk, the timing was highly suspicious. As if we weren't putting enough stress on the bird, dodging gunfire as well? What are people thinking? Oh yea, they weren't... After completing our work, we drove by to see if we could get the license numbers, but the plate was hidden from view. Regardless, they knew they were on record. As we passed back by two hours later, their camped had been cleared out.

The team. The job we do is a difficult one, often leaving us wiped at the end of the day. However, I do my best to try to make sure that the team is learning from the work and is able to gain experience which will help them in their future career. Most of that experience is gained through the direct performance of their job - prey and habitat surveying, bird identification, banding goshawks, drawing blood, etc. However, some tasks are above their direct responsibilities. This last weekend while we were banding nestlings, I offered to educate some of the team members on our climbing technique. They would need more experience before climbing into a live goshawk nest, but a local 10 foot training tree would help them appreciate the work. Mike and Michelle J took me up on my offer.

Michelle J getting ready to tie in a hard anchor.
Instructing Mike on the use of a Jumar for managing slings.

We also try to enjoy ourselves as much as possible. Mike, Emmy, and I took David and his family back to where Karyn and I found the moose carcass. Surprisingly we were able to find it. This moose appeared to be very healthy. The teeth were in great shape. A bit of velvet remaining on the antlers indicate a late summer, early fall death. Now what would kill a young, healthy, male moose before the start of the rut. It will remain a mystery, although the cynical side of me has a pretty good idea...

Mike, Emmy, and David with moose skull and antlers.

I hope to have more great news to share after out next bout in the woods!